[v3] PCI: mediatek-gen3: Avoid PCIe resetting via PCIE_RSTB for Airoha EN7581 SoC

Commit Message

Lorenzo Bianconi Nov. 13, 2024, 1:58 p.m. UTC

Airoha EN7581 has a hw bug asserting/releasing PCIE_PE_RSTB signal
causing occasional PCIe link down issues. In order to overcome the
problem, PCIE_RSTB signals are not asserted/released during device probe or
suspend/resume phase and the PCIe block is reset using REG_PCI_CONTROL
(0x88) and REG_RESET_CONTROL (0x834) registers available in the clock
module running clk_bulk_prepare_enable in mtk_pcie_en7581_power_up().

Introduce flags field in the mtk_gen3_pcie_pdata struct in order to
specify per-SoC capabilities.

Tested-by: Hui Ma <[e-mail]>
Signed-off-by: Lorenzo Bianconi <[e-mail]>
---
Changes in v3:
- cosmetics
- Link to v2: https://lore.kernel.org/r/[e-mail]

Changes in v2:
- introduce flags field in mtk_gen3_pcie_flags struct instead of adding
  reset callback
- fix the leftover case in mtk_pcie_suspend_noirq routine
- add more comments
- Link to v1: https://lore.kernel.org/r/[e-mail]
---
 drivers/pci/controller/pcie-mediatek-gen3.c | 60 ++++++++++++++++++++---------
 1 file changed, 42 insertions(+), 18 deletions(-)


---
base-commit: ff80d707f3cb5e8d9ec0739e0e5ed42dea179125
change-id: 20240920-pcie-en7581-rst-fix-8161658c13c4

Best regards,

Patch

diff --git a/drivers/pci/controller/pcie-mediatek-gen3.c b/drivers/pci/controller/pcie-mediatek-gen3.c
index 16a55711a7f3bdc8d6620029e3d2cfdd40b537b7..443072adb9b52a6934a5d1e38eb6fca5f86a1e13 100644
--- a/drivers/pci/controller/pcie-mediatek-gen3.c
+++ b/drivers/pci/controller/pcie-mediatek-gen3.c
@@ -128,10 +128,18 @@ 
 
 struct mtk_gen3_pcie;
 
+enum mtk_gen3_pcie_flags {
+	SKIP_PCIE_RSTB	= BIT(0), /* skip PCIE_RSTB signals configuration
+				   * during device probing or suspend/resume
+				   * phase in order to avoid hw bugs/issues.
+				   */
+};
+
 /**
  * struct mtk_gen3_pcie_pdata - differentiate between host generations
  * @power_up: pcie power_up callback
  * @phy_resets: phy reset lines SoC data.
+ * @flags: pcie device flags.
  */
 struct mtk_gen3_pcie_pdata {
 	int (*power_up)(struct mtk_gen3_pcie *pcie);
@@ -139,6 +147,7 @@  struct mtk_gen3_pcie_pdata {
 		const char *id[MAX_NUM_PHY_RESETS];
 		int num_resets;
 	} phy_resets;
+	u32 flags;
 };
 
 /**
@@ -405,22 +414,34 @@  static int mtk_pcie_startup_port(struct mtk_gen3_pcie *pcie)
 	val |= PCIE_DISABLE_DVFSRC_VLT_REQ;
 	writel_relaxed(val, pcie->base + PCIE_MISC_CTRL_REG);
 
-	/* Assert all reset signals */
-	val = readl_relaxed(pcie->base + PCIE_RST_CTRL_REG);
-	val |= PCIE_MAC_RSTB | PCIE_PHY_RSTB | PCIE_BRG_RSTB | PCIE_PE_RSTB;
-	writel_relaxed(val, pcie->base + PCIE_RST_CTRL_REG);
-
 	/*
-	 * Described in PCIe CEM specification sections 2.2 (PERST# Signal)
-	 * and 2.2.1 (Initial Power-Up (G3 to S0)).
-	 * The deassertion of PERST# should be delayed 100ms (TPVPERL)
-	 * for the power and clock to become stable.
+	 * Airoha EN7581 has a hw bug asserting/releasing PCIE_PE_RSTB signal
+	 * causing occasional PCIe link down. In order to overcome the issue,
+	 * PCIE_RSTB signals are not asserted/released at this stage and the
+	 * PCIe block is reset configuting REG_PCI_CONTROL (0x88) and
+	 * REG_RESET_CONTROL (0x834) registers available in the clock module
+	 * running clk_bulk_prepare_enable in mtk_pcie_en7581_power_up().
 	 */
-	msleep(100);
-
-	/* De-assert reset signals */
-	val &= ~(PCIE_MAC_RSTB | PCIE_PHY_RSTB | PCIE_BRG_RSTB | PCIE_PE_RSTB);
-	writel_relaxed(val, pcie->base + PCIE_RST_CTRL_REG);
+	if (!(pcie->soc->flags & SKIP_PCIE_RSTB)) {
+		/* Assert all reset signals */
+		val = readl_relaxed(pcie->base + PCIE_RST_CTRL_REG);
+		val |= PCIE_MAC_RSTB | PCIE_PHY_RSTB | PCIE_BRG_RSTB |
+		       PCIE_PE_RSTB;
+		writel_relaxed(val, pcie->base + PCIE_RST_CTRL_REG);
+
+		/*
+		 * Described in PCIe CEM specification sections 2.2 (PERST# Signal)
+		 * and 2.2.1 (Initial Power-Up (G3 to S0)).
+		 * The deassertion of PERST# should be delayed 100ms (TPVPERL)
+		 * for the power and clock to become stable.
+		 */
+		msleep(PCIE_T_PVPERL_MS);
+
+		/* De-assert reset signals */
+		val &= ~(PCIE_MAC_RSTB | PCIE_PHY_RSTB | PCIE_BRG_RSTB |
+			 PCIE_PE_RSTB);
+		writel_relaxed(val, pcie->base + PCIE_RST_CTRL_REG);
+	}
 
 	/* Check if the link is up or not */
 	err = readl_poll_timeout(pcie->base + PCIE_LINK_STATUS_REG, val,
@@ -1179,10 +1200,12 @@  static int mtk_pcie_suspend_noirq(struct device *dev)
 		return err;
 	}
 
-	/* Pull down the PERST# pin */
-	val = readl_relaxed(pcie->base + PCIE_RST_CTRL_REG);
-	val |= PCIE_PE_RSTB;
-	writel_relaxed(val, pcie->base + PCIE_RST_CTRL_REG);
+	if (!(pcie->soc->flags & SKIP_PCIE_RSTB)) {
+		/* Pull down the PERST# pin */
+		val = readl_relaxed(pcie->base + PCIE_RST_CTRL_REG);
+		val |= PCIE_PE_RSTB;
+		writel_relaxed(val, pcie->base + PCIE_RST_CTRL_REG);
+	}
 
 	dev_dbg(pcie->dev, "entered L2 states successfully");
 
@@ -1233,6 +1256,7 @@  static const struct mtk_gen3_pcie_pdata mtk_pcie_soc_en7581 = {
 		.id[2] = "phy-lane2",
 		.num_resets = 3,
 	},
+	.flags = SKIP_PCIE_RSTB,
 };
 
 static const struct of_device_id mtk_pcie_of_match[] = {